JSP: The Complete Reference in Java

Print QR in Java JSP: The Complete Reference

if (language != null && country != null) locale = new Locale(language, country); if (locale == null) locale = LocalegetDefault(); ResourceBundle RB = ResourceBundlegetBundle ("jspcrsessionswelcome", locale); // Store the resource bundle as an attribute of the request requestsetAttribute("RB", RB); %>

getLocalejsp uses requestgetCookies() to get an array of all the cookies in the request It looks through the list for the language and country cookies If getLocalejsp finds them, it creates a javautilLocale for that language and country If the cookies aren t found (which is the case the first time the user visits the page), it uses the default locale Either way, it loads the resource bundle associated with this application and locale, and then stores the bundle as a request attribute After it returns from the <jsp:include>, indexjsp retrieves the resource bundle and uses ResourceBundlegetString() to get the translated text indexjsp calls another utility page named languageBarjsp to create the language selection hyperlinks Stored in each hyperlink is the URL for the main page (including any parameters), as well as the language and country codes Here is languageBarjsp:

<%@ page session="false" %> <%@ page import="javautil*" %> <% String thisURL = HttpUtilsgetRequestURL(request)toString(); thisURL = javanetURLEncoderencode(thisURL); Object[][] locales = {new Locale("en", {new Locale("de", {new Locale("es", {new Locale("fr", {new Locale("it", }; { "US"), "DE"), "ES"), "FR"), "IT"),

"English"}, "Deutsch"}, "Espa ol"}, "Fran ais"}, "Italiano"},

for (int i = 0; i < localeslength; i++) {

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Locale locale = (Locale) locales[i][0]; String name = (String) locales[i][1]; StringBuffer sb = new StringBuffer(); if (i > 0) sbappend(" | "); sbappend("<A HREF=\"setPreferencesjsp cameFrom="); sbappend(thisURL); sbappend("&language="); sbappend(localegetLanguage()); sbappend("&country="); sbappend(localegetCountry()); sbappend("\""); sbappend(">"); sbappend(name); sbappend("</A>"); outprintln(sb); } %> JSP IN ACTION

The hyperlinks invoke setPreferencesjsp, which generates the appropriate language and country cookies, and then adds them to the outgoing response header Next, the JSP redirects the browser back to the calling page, as shown in the following:

<%@ page session="false" %> <% // Set cookies for language and country final int ONE_YEAR = 60 * 60 * 24 * 365; String[] parms = { "language", "country" }; for (int i = 0; i < parmslength; i++) { String name = parms[i]; String value = requestgetParameter(name); if (value != null) { Cookie cookie = new Cookie(name, value); cookiesetMaxAge(ONE_YEAR); responseaddCookie(cookie); } }

// Redirect back to the calling JSP String cameFrom = requestgetParameter("cameFrom"); if (cameFrom == null) cameFrom = requestgetContextPath(); responsesendRedirect(cameFrom); %>

The indexjsp page originally comes up in the default locale, as shown in Figure 14-3 If the user clicks the French hyperlink, the setPreferencesjsp page is invoked, which redirects the browser back to indexjsp, this time with cookies attached The result is the French version of the page, seen in Figure 14-4 If the user visits the site the next day, the language preference is remembered and applied The main problem with cookies is users can and do turn off their browser s cookie support, usually for privacy reasons This means the application must be prepared to do its work some other way if it cannot use cookies

Figure 14-3

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Figure 14-4

So far, we ve examined two general approaches to session tracking, both of which involve the client remembering the state: I Have the client store all session data and return it to the server with each request I Have the client store a session identifier and have the server handle the rest While the first method may be easier to implement, the second, in general, offers more flexibility and scalability We have seen that hidden fields, URL rewriting, and cookies can all be used to support either method, to some extent But most servlets and JSP pages that need to use sessions can take advantage of a higher-level approach: the HttpSession API Three classes are in the javaxservlethttp package that comprise the session API: I HttpSession An interface that acts like a Map or Hashtable, able to store and retrieve objects by name A session is created by a call to HttpServletRequestgetSession() and persists until it times out or is shut down by a servlet participating in the session Incoming HTTP requests that carry the session identifier are automatically associated with the session